No with same amount allies i was getting 17.6m per hit in ambush but wen i built coe on highland it became 14m per hit Shall i sell coe :-(
Try dancing to a tougher song. Like the mamba. As your strength overtakes your target your plunder will lessen. This is to encourage players to seek bigger targets while not bullying small ones.
I have to agree with Santa and GU on this one. I just don't think that 13 billion in allies is enough for your stats to be at max plunder. I would suggest giving Santa's test a try. Also you should read the stickied guide in this section about max plunder.
OP, don't worry, your plunder decrease happened to all of us. It is sort of a weird glitch that happens around your stats. You build and stay at Mac plunder but you notice a small drop in plunder.... Basically it just happens. It only happens this one time, just keep building and stay max plunder and it will go up again. I don't think this glitch happens With spies/hansels, but it happened to all of us attk builds.